Was very happy to receive my iSonic 76 yesterday, but none of my fins would fit including drake fins from previous years (the drake fin provided with the board did however). I've spent the last two hours attempting to carefully sand the fin box (at least I've got little fingers to fit in the box), as if i sanded my fins further they would be too loose in my other boards.

I know there will always be manufacturing tolerances, but why is the accompanying fin also smaller. Are you using different molds this year... they seem to be shrinking each year. Just a little frustrating and fiddly... especially if I'll have to do this with all new boards.

Well, hopefully the board sails like a smaller version of the 87 and it will all be worthwhile.

Your post has brought up a concern that I think is rather important, at least from my perspective. When you think about all the tolerances between different boards and fins, it can be too challenging, particularly if also working the special screws needed between US and metric sized fins.

The last thing a customer wants are tolerance differences in the board's integral fin boxes. I can say with my boards that there has been great synergy over more than 15 years. Quite frankly, the Water Rat Tuttle boxes are incredibly consistent, and that has made quite a difference integrating different fins and brands over the years. No one wants to start having to change things that you know are right from the past. If one has a cache of fins over time, especially ones that have worked in so many boards, you certainly don't want to start hacking things with abandon.

Recently I ordered a few Techtonic fins and they all required serious sanding to fit into my F2 Missile XS, SX M & iSonic 87. Fortuneately the fins boxes seem the same throughout as all fins fit the same in the various boards.

In addition to this, the fin supplied with my F2 Missile XS required extensive sanding to fit the board it was supplied with!

Now I have to admit that the stock fin provided with the iSonic fitted perfectly and so this thread is aimed at F2 and Techtonics so really shouldn't be here but perhaps some users of this forum would comment if they have had the exact same problems.

Surely it can't be that hard for all fin and board manufacturers to tighten up in this area.

Regarding Tectonics fins, I've got six of them with Tuttle bases and I've never had to sand a single one. They have always worked perfectly with no modifications needed. I also find True Ames fins to be right on with the tolerances of their fins. In addition, I have a number of Lessacher fins too, and they all work well, except one is a bit on the tight side, but it still fits.

So all and all, my experiences support a position that fin manufacturers are doing a great job with their tolerancing. So, I must consider your findings to be very unusual, at least with Tectonics fins. I could be mistaken, but isn't the F2 brand using Powerbox in their small and medium boards with cavity type boxes?

If the tolerances on the fin boxes are so sloppy, what about the shapes of the boards?? I wonder how consistent the rocker lines are...
My Mike Labs and Tectonics fins fit like swiss watch parts. Would you tolerate a car tire that doesn't fit the rim?

I maybe wrong but I believe SB tightened up on finbox tolerences a couple of years back bringing the boxes closer to spec. If they were too wide before then some sanding may be required to fit newer boards.

Looking at the hire/demo kit at brog reveals that all the SB fins seem to fit all the boards so tolerences must be quite good.

Whenever I buy select fins they do require quite a bit of fitting but I would rather they be too tight than too loose.
All fins require some fitting, some more than others.

I would be miffed if I bought a board and the stock fin needed fitting though.

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With an electric sander the process doesn't take too long so I'm not overly bothered the time, suffice to say I've another Falcon in the post to me.

My concern however is that you could sand too much off one side or do it at an angle resulting in a fin which is very precise in its design not having the expected laminar flow over it, although I doubt this would have any noticeable effect.

I have had the same problem with Tectonic fins as well as Vector fins,all needed sanding to fit into my boards.The same goes for friends who have purchased these fins.

Recently I had to sand down a Tectonic fin to fit a Naish board. It's no big deal, though. I was a bit frightened that I took too much off with the disk sander on the electric drill, but it fits quite well in the box now. I can't see why you guys find this important.